APOD: 2006 March 23 - Inflating the Universe No Center http://www.astro.ucla.edu/~wright/nocenter.html http://www.astro.ucla.edu/~wright/infpoint.html Also see Ned Wright's Cosmology Tutorial http://www.astro.ucla.edu/~wright/cosmolog.htm http://www.astro.ucla.edu/~wright/cosmology_faq.html http://www.astro.ucla.edu/~wright/CosmoCalc.html WMAP: Foundations of the Big Bang theory http://map.gsfc.nasa.gov/m_uni.html WMAP: Tests of Big Bang Cosmology http://map.gsfc.nasa.gov/m_uni/uni_101bbtest.html Cosmology News Big Bang Acoustics: Movie and Sound Files History of the Universe from This Week's Finds in Mathematical Physics (Week 196) -- First of all, we only "know" anything about the world on the basis of various assumptions. If our assumptions turn out to be wrong, our "knowledge" may turn out to be wrong too. Even worse, our favorite concepts may turn out to be meaningless, or meaningful only under some restrictions. So, when we talk about what happened in the first microsecond after the Big Bang, we're not claiming absolute certainty. Instead, we're using various widely accepted assumptions about physics to guess what happened. Given these assumptions, the concept of "the first microsecond after the Big Bang" makes perfect sense. But if these assumptions are wrong, the whole question could dissolve into meaninglessness. That's just a risk we have to run. What are these assumptions, exactly? They include: 1.  General Relativity 2.  Standard Model of particle physics               supplemented by 3.  Dark Energy (a non zero cosmological constant) 4.  Dark Matter (electromagnetic non interaction) Assumptions 3 and 4 are the ones most people like to worry about, because our only evidence for them comes from cosmological observations, and if they're true, they probably require some sort of modification of the Standard Model. But if we don't make these assumptions, our model of cosmology just doesn't work... while if we *do*, it seems to work quite well. In fact, the WMAP experiment gives a lot of new evidence that it works surprisingly well. 1.  The polarization of the microwave background anisotropy coming from scattering by electrons 400 million years after the Big Bang has been detected. This is evidence for an early generation of stars existing 2 to 3 times earlier than any object yet observed. 2.  The WMAP data agree with previous work showing the Universe is flat and in an accelerating expansion. 3.  The WMAP data give the most precise values for the density of ordinary [baryonic] matter made of protons and neutrons: 0.4 yoctograms per cubic meter, and for the total of dark and baryonic matter: 2.5 yoctograms per cubic meter. These correspond to omega_b = 0.0224 +/- 0.0009 and omega_m = 0.135 +/- 0.009. 4.  The WMAP data give the most precise value for the age of the Universe: 13.7 +/- 0.2 Gyr. The Hubble constant is Ho = 71 +/- 4 km/sec/Mpc, and the vacuum energy density corresponds to lambda = 0.73 +/- 0.04. Wilkinson Microwave Anisotropy Probe (WMAP)     Bibliography of WMAP Science Team Publications     Foundations of the Big Bang theory     Tests of Big Bang Cosmology     Implications for Cosmology (pdf) Ned Wright's Cosmology Tutorial - Cosmology is the study of the origin, current state, and future of our Universe. This field has been revolutionized by many discoveries made during the past century. My cosmology tutorial is an attempt to summarize these discoveries. It will be "under construction" for the foreseeable future as new discoveries are made. I will attempt to keep these pages up-to-date as a resource for the cosmology courses I teach at UCLA. The tutorial is completely non-commercial, but tax deductible donations to UCLA are always welcome.   Javascript calculator of the many distances involved in cosmology Max Tegmark's CMB analysis center: EXPERIMENTS -- His research is focused on precision cosmology, e.g., combining theoretical work with new measurements to place sharp constraints on cosmological models and their free parameters. Dark matter maps reveal cosmic scaffolding - Ordinary baryonic particles (such as protons and neutrons) account for only one-sixth of the total matter in the Universe. The remainder is a mysterious "dark matter" component, which does not interact via electromagnetism and thus neither emits nor reflects light. As dark matter cannot be seen directly using traditional observations, very little is currently known about its properties. It does interact via gravity, and is most effectively probed through gravitational lensing: the deflection of light from distant galaxies by the gravitational attraction of foreground mass concentrations. This is a purely geometrical effect that is free of astrophysical assumptions and sensitive to all matter -- whether baryonic or dark. Here we show high fidelity maps of the large-scale distribution of dark matter, resolved in both angle and depth. We find a loose network of filaments, growing over time, which intersect in massive structures at the locations of clusters of galaxies. Our results are consistent with predictions of gravitationally induced structure formation, in which the initial, smooth distribution of dark matter collapses into filaments then into clusters, forming a gravitational scaffold into which gas can accumulate, and stars can be built. Laser Interferometer Gravitational-Wave Observatory - Gravitational waves offer a remarkable opportunity to see the universe from a new perspective, providing access to astrophysical insights that are available in no other way. The initial LIGO gravitational wave detectors have started observations, and are already yielding data that are being interpreted to establish new upper limits on gravitational-wave flux. The sensitivity of the initial LIGO instruments is such that it is perfectly possible that discoveries will be made. If they succeed, there will be a strong demand from the community to improve the sensitivity allowing more astrophysical information to be recovered from the signals. If no discovery is made, there will be no lesser urgency to improve the sensitivity of the instrument to the point where there is a general consensus that gravitational waves will be detected often and with a good signal-to-noise ratio. The development of the next generation of instrument must be pursued aggressively to make the transition from the initial to the Advanced detector in a timely way - after the complete science run of the initial detector, but as quickly as possible thereafter. The Elegant Universe Transcript   by Brian Greene Interview with Physicist Steven Weinberg     http://www.meta-library.net/transcript/wein-body.html QUESTION: You have written that the more comprehensible the universe becomes the more pointless it seems. Could you explain what you mean by that? DR. WEINBERG: Years ago I wrote a book about cosmology, and near the end I tried to summarize the view of the expanding universe and the laws of nature. And I made the remark - I guess I was foolish enough to make the remark - that the more the universe seems comprehensible the more it seems pointless. And that remark has been quoted more than anything else I've ever said. It's even in Bartlett's Quotations. I think it's been the truth in the past that it was widely hoped that by studying nature we will find the sign of a grand plan, in which human beings play a particularly distinguished starring role. And that has not happened. I think that more and more the picture of nature, the outside world, has been one of an impersonal world governed by mathematical laws that are not particularly concerned with human beings, in which human beings appear as a chance phenomenon, not the goal toward which the universe is directed. And for some this has no effect on their religion. Their religion never looked for any kind of point in nature. For others this is appalling, the idea that all of the stars and galaxies and atoms are going about their business, and it's just by accident that here on this solar system the peculiar chemical properties of DNA acting over billions of years have produced these people who have been able to talk and look around and enjoy life. For some people that picture is antithetical to the view of nature and the world that their religion had given them. QUESTION: Do you believe then there is no overall point to the universe? DR. WEINBERG: I believe that there is no point in the universe that can be discovered by the methods of science. I believe that what we have found so far, an impersonal universe in which it is not particularly directed toward human beings is what we are going to continue to find. And that when we find the ultimate laws of nature they will have a chilling, cold impersonal quality about them. I don't think this means [however] there's no point to life. Usually the remark is quoted just as it stands. But if anyone read the next paragraph, they would see that I went on to say that if there is no point in the universe that we discover by the methods of science, there is a point that we can give the universe by the way we live, by loving each other, by discovering things about nature, by creating works of art. And that -- in a way, although we are not the stars in a cosmic drama, if the only drama we're starring in is one that we are making up as we go along, it is not entirely ignoble that faced with this unloving, impersonal universe we make a little island of warmth and love and science and art for ourselves. That's not an entirely despicable role for us to play. http://www.npr.org/templates/story/story.php?storyId=1569860     © Copyright 2010 - Samuel J. Wormley   by swormley1@gmail.com